Question 1

Which of the following best explains why lightning, as seen in the first image, is considered a demonstration of electric forces in nature?

Accepted Answer

Lightning is a discharge of electric charge due to the buildup of opposite charges in clouds and the ground, resulting in a strong electric force.

Question 2

An electroscope, as shown in the second and third images, is used to detect electric charge. What happens to the leaves of the electroscope when a negatively charged rod is brought near (but does not touch) the knob?

Accepted Answer

The leaves move apart because electrons are repelled from the knob to the leaves, making both leaves negatively charged.

Question 3

Which of the following statements about charge polarization, as illustrated in the fourth image, is correct?

Accepted Answer

Polarization is a separation of positive and negative charges within a neutral object, causing one side to be slightly more positive or negative.

Question 4

A positively charged rod is brought near a neutral metal sphere. What is the net force acting on the sphere, and why?

Accepted Answer

There is an attractive force due to polarization; the electrons in the sphere are attracted to the rod, creating a net force toward the rod.

Question 5

Which equation correctly represents Coulomb’s Law for the magnitude of the force between two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$?

Accepted Answer

$$F = K \frac{|q_1$ q_2$|}{r^2$}$$

Question 6

Two identical metal spheres are touching. A positively charged rod is brought near one sphere, and then the spheres are separated while the rod is still present. What is the final charge on each sphere after the rod is removed?

Accepted Answer

One sphere is positively charged and the other is negatively charged.

Question 7

A glass bead with mass $$2.0 	imes 10$$^{-6}$$ kg and charge +10$ nC is placed 1.0 cm below a plastic bead with charge -10$ nC. Using K = 8.99$$ 	imes $$10^9 N m$^2/C$^2$$, what is the magnitude of the electrostatic force between the beads?

Accepted Answer

$$F = 9.0 	imes 10$$^{-3}$$ N

Question 8

If the distance between two point charges is halved, how does the magnitude of the electrostatic force between them change?

Accepted Answer

It becomes four times as large.

Question 9

Which of the following best describes the force between two charges of $$+2$$ μC and $$-2$$ μC separated by 0.1 m?

Accepted Answer

The force is attractive and given by $$F = K \frac{|q_1$ q_2$|}{r^2$}.$$

Question 10

A neutral insulator is brought near a positively charged rod. What happens at the atomic level inside the insulator?

Accepted Answer

Atoms in the insulator become polarized, with their negative charges slightly closer to the rod than their positive charges.

Question 11

A rod attracts a positively charged hanging ball. Which of the following could be the charge on the rod?

Accepted Answer

The rod could be either negatively charged or neutral.

Question 12

Which of the following is a correct statement of Newton’s third law as it applies to electrostatic forces?

Accepted Answer

The force that charge 1 exerts on charge 2 is equal in magnitude and opposite in direction to the force that charge 2 exerts on charge 1.

Question 13

A positively charged rod is brought near the knob of a neutral electroscope. What happens to the electrons in the electroscope?

Accepted Answer

Electrons move from the leaves to the knob, causing the leaves to become more positively charged and repel each other.

Question 14

Which of the following best describes charging by induction?

Accepted Answer

Charging an object by bringing it near a charged object and then separating it while polarized, without direct contact.

Question 15

In the example of lifting a glass bead, the electrostatic force is found to be 60 times greater than the gravitational force. If the distance between the beads is increased to 5 cm, will the glass bead still leap upwards?

Accepted Answer

No, because the electrostatic force decreases with the square of the distance and may no longer overcome gravity.

Question 16

Which of the following is NOT a correct step in solving problems using Coulomb’s Law?

Accepted Answer

Add the forces as scalars without considering direction.

Chapter 22: Electric Charges and Forces – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards